黒沼 尊紀

The occurrence of tipburn is a severe problem in horticulture crop production. A previous study suggested that, in lisianthus, tipburn is caused by imbalanced calcium (Ca) distribution. However, there are few studies on the effects of other cations on tipburn incidence in lisianthus cultivars. In this study, to determine the effect of Magnesium (Mg) concentration in nutrient solution on tipburn incidence and Ca and Mg acquisition, three lisianthus cultivars (‘Celeb Wine’: CW, ‘Reina White’: RW, and ‘Voyage Peach’: VP) were cultivated under different Mg concentrations in nutrient solution (12 ppm, 34.7 ppm, and 75.4 ppm). Under high nutritional Mg concentrations, CW and RW had significantly decreased tipburn severity, while VP showed no significant differences in tipburn severity among the treatments. Total Ca concentrations in all cultivars significantly increased at higher nutritional Mg concentrations, which indicated that Mg application in lisianthus cultivars promoted Ca acquisition. Furthermore, it was suggested that CW and RW had the ability to distribute increased Mg to the tip of the upper leaves, thereby promoting Ca distribution. Thus, a decrease in tipburn severity in CW and RW at higher nutritional Mg concentrations appeared to occur.

The occurrence of calcium (Ca2+) deficiency disorders is a severe problem in the production of horticulture crops. Recently, several studies have investigated the role of gene expression in Ca2+ deficiency disorders and/or Ca2+ accumulation, providing an indication of the mechanism of Ca2+ deficiency disorders at the genetic level. To determine the relation between gene expression and the occurrence of Ca2+ deficiency disorders, we conducted a systematic review of the literature using the Preferred Reporting Items for Systematic Reviews and Meta-analyses protocol. In our initial search, we extracted studies investigating the relationships between Ca2+ deficiency disorders (tipburn and blossom-end rot) and gene expression. In our second search, we extracted studies involving functional analyses of the genes associated with Ca2+ deficiency and/or Ca2+ accumulation in plant organs. Thirty-seven articles were extracted from both searches. Studies on Ca2+ movement-related genes (Ca2+ antiporters, calreticulin, Ca2+ pumps, Ca2+ channels, and pectin methylesterases) accounted for the majority of these articles. Particularly, the effects of the expression of CAXs (Ca2+/H+ antiporters) and CRT (calreticulin) on the occurrence of Ca2+ deficiency disorders were demonstrated in studies extracted from both searches. Further research focusing on these genes may reveal the causative genes for Ca deficiency disorders in different horticulture crops. We hope that the knowledge synthesized in this systematic review will contribute to the accumulation of further knowledge and elucidation of the causes of Ca2+ deficiency disorders.

Occurrence of tipburn is a severe problem in the production of lisianthus cultivars. Previous studies have shown excessive Ca accumulation in the roots of tipburn-damaged cultivars, where the distribution of Ca to the tips of the top leaves is inhibited. However, few studies have investigated the association between Ca accumulation and gene expression in horticultural crops. To provide a list of candidate target genes that might be causing the excessive Ca accumulation in roots, we focused Ca2+ transporter and pectin methylesterase (PME) genes and RNA-seq of upper leaves and roots in tipburn-occurrence cultivar (“Voyage peach”: VP) and non-occurrence cultivar (“Umi honoka”: UH) was conducted. In both the upper leaves and roots of VP, genes encoding the glutamate receptors (GLRs), cation/Ca2+ exchangers 4 (CCX4), Na+/Ca2+ exchanger-like protein (NCL), and PMEs were upregulated, and a gene encoding the cyclic nucleotide-gated ion channel 9 (CNGC9) was downregulated. In contrast, genes encoding the vacuolar cation/proton exchanger 5 (CAX5), calcium-transporting ATPase 1 and 12 (ACA1 and ACA12) showed differential expression in each organ. Among them, only CAX5 was upregulated and ACA12 was downregulated in the roots of VP. Based on these results, we suggested that CAX5 and ACA12 are the candidate genes causing the excessive Ca accumulation in the roots of tipburn-occurrence lisianthus cultivars. Future studies should investigate the temporal changes in gene expression using quantitative PCR and conduct functional analysis of candidate genes in tipburn-damaged lisianthus cultivars.

In lisianthus cultivars, the occurrence of tipburn is known to adversely affect quality and yield. However, information concerning the responses of tipburn incidence to different levels of Ca is limited. In addition, only a few studies have investigated the effect of potassium (K) concentration on Ca acquisition and distribution in lisianthus. To address this knowledge gap, we investigated tipburn incidence in three lisianthus cultivars (Umi honoka (UH), Reina white (RW), and Voyage peach (VP)) and the Ca and K concentrations in them under different concentrations of Ca supply (40, 80, and 120 ppm). These cultivars exhibited different responses to different concentrations of Ca supply. Tipburn was not observed in UH. In RW, tipburn incidence and severity significantly decreased with an increase in nutritional Ca concentration, because the Ca concentration in the tips of the top leaves significantly increased with Ca concentration. By contrast, in VP, tipburn incidence under all treatments was 100%, and there was no significant difference in the Ca concentration in the tips of the top leaves among the treatments, but the total Ca concentration significantly increased. VP was the only cultivar that significantly acquired and accumulated more Ca in the roots with an increase in nutritional Ca concentration. Overall, excessive Ca accumulation in the roots under high-Ca conditions inhibits the distribution of Ca to the tips of the top leaves and eventually manifests as tipburn in the cultivar. In addition, our results suggested that the content ratio of K in the nutrient solutions did not prevent Ca acquisition and distribution in lisianthus cultivars and that the K concentration has a negligible effect on the occurrence of tipburn.

Population growth and increased stress caused by urbanization have led to social problems that are predicted to intensify in the future. In these conditions, the recently established ”nature therapy” has revealed that an environment rich in various plant life significantly contributes to the relief of physical and mental stress. Meanwhile, from the perspective of reduction in the energy required for transportation and the retention of plant freshness, urban horticulture, in which plant life exists harmoniously with the city, has attracted considerable attention. Interactions between humans and plants in urban horticulture are considered to contribute to the good health and wellbeing of people. Therefore, we incorporate human-centered thinking based on nature therapy into horticultural produce-centered thinking based on conventional urban horticulture. By introducing a pioneering urban horticulture plant factory as an example, we propose the possibility of sustainable urban horticulture based on nature therapy.

Distinction of intergeneric hybrids between Argyranthemum frutescens (L.) Sch. Bip. and Rhodanthemum gayanum (Cross. & Durieu) B.H. Wilcox, K. Bremer & Humphries is important for the development of new intergeneric hybrids. The aim of this study was to develop a simple and cost-effective DNA marker to distinguish between a large number of putative hybrids of A. frutescens x R. gayanum during primary selection. We designed sequence-characterized amplified region (SCAR) markers based on the genetic sequences of the internal transcribed spacer (ITS) region for A. frutescens and R. gayanum. Specific SCAR markers for A. frutescens amplified bands in A. frutescens and hybrids but not in R. gayanum. In contrast, specific SCAR markers for R. gayanum amplified bands in R. gayanum and hybrids but not in A. frutescens. Additionally, we confirmed the reproducibility of the SCAR marker using 31 cultivars. The findings demonstrated that these SCAR markers could be used to distinguish putative hybrids between A. frutescens and R. gayanum. This is the first report of the development of a SCAR marker to facilitate distinction of these hybrids.

In this study, we performed intergeneric crosses between Argyranthemum frutescens (L.) Sch. Bip. and seven perennial species of closely related genera [Artemisia absinthium L., Chrysanthemum lavandulifolium (Fisch. ex Trautv.) Makino x Chrysanthemum x mon:fawn Ramat., Dimorphotheca sinuata DC., Osteospermum ecklonis (de Candolle) Norlindh, Pericaiis hybrida B. Nord., Rhodanthemum gayanum (Cross. & Du rieu) B.H. Wilcox, K. Bremer & Humphries., and Rhodanthemum hosmariense (Ball) B.H. Wilcox, K. Bremer & Humphries.). Using an embryo culture technique to generate intergeneric hybrids, we produced two putative hybrids from the crosses between A. fruteseens and R. gayanum. In the putative hybrid derived from the cross between A. frutescens 'Brilliant rouge' x R. gayanum 'Elf pink', its ligulate flower color was similar to the 'Brilliant rouge' seed parent while the composition and total amount of anthocyanidins and/or leucoanthocyanidins were different. In the putative hybrid derived from the cross between A. frutescens 'Sunday ripple' and R. gayanum 'African eyes', its ligulate flower color differed from those of the parents. The ligulate flowers of the parents were white and produced no anthocyanidins, whereas the putative hybrids had light pink ligulate flowers and produced three anthocyanidins pigments [pelargonidins (including pelargonidin and/or leucopelargonidin), cyanidins (including cyanidin and/or leucocyanidin, peonidin), and delphinidins (including delphinidin and/or leucodelphinidin, malvidin)]. In addition, the cleaved amplified polymorphic sequence (CAPS) markers (Afl ID developed in this study confirmed that the putative hybrids were intergeneric hybrids of A.fruteseens x R. gayanum. Therefore, these CAPS selection markers can be used to determine whether plants resulting from crosses are hybrids.

Sedum species, which utilize crassulacean acid metabolism (CAM) photosynthetic pathway, have been the most commonly used plants in extensive green roofs. Previous investigations on Sedum green roofs have focused on their establishment and survival under drought conditions. Several Sedum species have been described as "inducible type of CAM" plants, suggesting that their photosynthetic and transpiration rates under wet conditions might greatly affect the carbon sequestration and the cooling effect of a Sedum green roof. Therefore, we investigated the photosynthetic and transpiration rates of three Sedum species (Sedum japonicum Siebold ex Miq., Sedum lineare Thunb., and Sedum sarmentosum Bunge) under wet and dry treatments. All three Sedum species exhibited CO2 uptake only during the light period under wet conditions as well as under dry treatment for several days after irrigation. Moreover, in the wet treatment, their photosynthetic and transpiration rates were found to be similar to those of the other green roof plants, Zoysia matrella (L.) Merr. and Ophiopogon japonicus (Thunb.) Ker Gawl. Thus, we suggest that the carbon sequestration and the cooling effect of the Sedum green roofs are equivalent to those of the green roofs utilizing the other plant under wet conditions from the standpoint of physiological traits.

The physiological and morphological traits of green roof plants are key to understanding the environmental benefits of green roofs. However, the comparative investigation of physiological and morphological traits of green roof plants is limited. Moreover, there have been few studies on the relevance of physiological and morphological traits and competence for carbon sequestration of green roof plants. In particular, Sedum L. species are generally regarded as crassulacean acid metabolism (CAM) plants, but several Sedum species are recognized as having an "inducible type of CAM.'' These plants are C-3 and C-4 plants, with the ability to switch their carbon metabolism to the CAM pathway. In the case of Sedum, the inducer of CAM is drought stress. This observation suggests that differences in water regimes result in physiological and morphological changes that may have a considerable effect on the environmental benefits of Sedum green roofs. The purpose of this study is to compare the physiological and morphological traits of four green roof plants and discuss the influence of these traits on their environmental benefits under a controlled environmental system. In addition, we attempted to clarify the relevance of physiological and morphological traits and competence for carbon sequestration in each plant using growth analysis. We used Sedum mexicanum Briton, Sedum aizoon L., Zoysia matrella (L.) Merr., and Ophiopogon japonicus (Thunb.) Ker Gawl. in this study, and only the two Sedum species were assigned treatments with different frequency of irrigation to investigate physiological and morphological responses and variation in carbon sequestration. The two Sedum species exhibited the C-3 photosynthetic pathway in wet and dry treatments, implying the inducible type of CAM. Morphological responses of the two Sedum species were significantly affected by the different frequencies of irrigation; plants responded to increases in below-ground resources (water and nutrients) with increased biomass allocation of leaves and stems. Owing to these physiological and morphological responses in the wet treatment, transpiration rates and competence for carbon sequestration [relative C sequestration rate per whole-plant C content (RGR(c))] of the two Sedum species were higher than those of Z. matrella and O. japonicus. This result suggested that the cooling effect and carbon sequestration of Sedum in wet and increased nutrient conditions are equivalent to those observed in other plants. In addition, the net assimilation rate (NAR(c)) and leaf area ratio per whole-plant C content (LAR(c)) were significantly correlated with photosynthetic rates and biomass allocation. Thus, it became clear that growth analysis can reveal the relevance of physiological (NAR(c)) and morphological (LAR(c)) traits and RGRc. Our results will serve as a baseline of the physiological and morphological traits and carbon sequestration of green roof plants and contribute to more suitable design and maintenance of vegetation in green roofs.

耐塩性と観賞性の評価，および生理的耐塩性機構の定量化を目的として，観賞植物3種に対し30日間の塩処理を行い，それらを塩生植物と比較した。シロタエギクは塩生植物に近い耐塩性を有し，観賞性も損なわれなかった。また，シロタエギクはNa⁺ 排除型，カレープランツはNa⁺ 蓄積型に分類されることが示された。本研究より，観賞植物に対し複数の耐塩性評価指標を適用することで，観賞植物と塩生植物の比較，および耐塩性と観賞性の同時評価が可能になった。また，耐塩性機構の特徴を把握することで，緑化目標に即した塩害地における植物種の選択が可能になると考えられた。

屋上緑化に用いられる数種の軽量土壌は，施工初期に雨水や灌水により，多くの栄養塩類が流出することが明らかとなっている。そこで本研究は，環境負荷を低減した新たな屋上緑化システムを検討するため，水耕栽培システムを用いて実験を行った。その結果，水耕栽培システムを用いた屋上緑化は，観賞性を保ちながら，慣行法(軽量土壌)よりも灌水量および栄養塩類の流出量を削減することが明らかとなった。

コウライシバを植栽した屋上緑化薄層基盤軽量土壌の経年変化を調査した。芝の生育，土壌物理性に経年的な変化は見られなかった。土壌有機物は施工後から増加する傾向にあり，栄養塩類含有量は，ゴルフ場グリーンの土壌診断基準値とほぼ同等であった。また，未使用の軽量土壌中の栄養塩類量は施工後の含有量より有意に高く，施工後は経年的に減少した。追肥の有無による栄養塩類量の差は確認されなかった。これらのことから，屋上独自の環境を考慮し，その管理目標に適した施肥管理を行う必要があることが明らかになった。